Just compared Kodak's 14n/n, Fujifilm S2, and Nikon D70. I didn't pay
attention to check it but it seems the larger the image sensor, the
larger the image in the TTL viewfinder.

Yes, of course, since they are retro-fit to the originally fixed size
image, and what shown in the DSLR is essentially the cropped-down.

Just curious, is this true for all DSLRs? Any DSLR has the dedicated
TTL viewfinder so that there is no need to suffer this cropped-down
TTL VF image? What about Olympus? Anything (other than Kodak-14n) has
the TTL feel like a real 35mm SLR?